Computing devices have made significant contributions toward the advancement of modern society and are utilized in a number of applications to achieve advantageous results. Numerous devices, such as digital cameras, computers, game consoles, video equipment, hand-held computing devices, audio devices, telephones, and navigation systems have facilitated increased productivity and reduced costs in communicating and analyzing data in most areas of entertainment, education, business and science. The digital camera and camcorders, for example, has become popular for personal use and for use in business.
FIG. 1 shows an exemplary digital camera according to the conventional art. The digital camera 100 typically includes one or more lenses 110, one or more image sensor arrays 130, an analog-to-digital converter (ADC) 140, a digital signal processor (DSP) 150 and one or more computing device readable media 160. The image sensor 130 includes a two-dimension array of hundreds, thousand, millions or more of imaging sensors, which each convert light (e.g. photons) into electrons. The array of sensor cells are typically arranged in a pattern of red, green and blue cells The image sensor 130 may be a charge coupled device (CCD), complementary metal oxide semiconductor (CMOS) device, or the like. Referring now to FIG. 2, an exemplary Bayer CMOS sensor array is illustrated. In the array, rows of red and green sensor cells 210, 220 are interleaved with rows of blue and green sensor cells 230, 240. In a CMOS sensor array, the sensor cells are separated by sense lines 250, 260. In CCD arrays, sense lines are not formed between the rows and/or columns of cells, therefore the cells are formed right next to each other.
A continual issue when dealing with cameras and other optical devices is the distortion introduced by the lens, image sensor arrays and the like of the camera itself. Many different kinds of distortion can occur, and are familiar problems for camera designers and photographers alike.
Several approaches are traditionally used, when correcting distortion. In more expensive cameras, such as single-lens reflex (SLR) cameras, combinations of lenses are used in sequence, with each additional piece of glass often designed to reduce or eliminate a particular type of distortion. Less expensive cameras offer correspondingly fewer hardware fixes for the distortion introduced by their lenses, with integrated solutions, such as mobile phone cameras, having almost no inherent distortion correction.
Distortion can also be corrected after an image has been captured. Digital imagery, such as the pictures and video captured by digital cameras and camcorders, can be manipulated after the image has been taken, and the distortion introduced by the camera itself can be reduced.
Referring again to FIG. 1, light coming through the lens 110 and forming an image of on the image sensor 130 will typically be unevenly attenuated across the image plane and color spectrum due to imperfections in the lens 110, filter 120 and image sensor 130. Therefore, the DSP 150 applies a high order two-dimensional polynomial interpolation across the image plane. The two-dimensional polynomial f(x,y), however, can be expensive to calculate and use. Furthermore, the two-dimensional polynomial are often numerically unstable and posses other undesirable properties. Accordingly, there is a continuing need for improved imaging processing techniques that provide image intensity correction.